Smelting volatilizable metals



Patented Feb. 16,. 19,26. a

WILLIAM A. OGG OF NEWTON, MASSACHUSETTS.

smmrme vota'rrrrzanrn METALS.

Application filed May 1a, 1925. Serial No. 30,914.

To all whom it may concern:

Be it known that I, WILLIAM A. Gas, a citizen of the United States, and a resident of Newton, county of Middlesex, and State of Massachusetts, have invented an Improvement in Smelting Volatilizable Metals, of which the following description, in connection with the accompanying drawings, is a specification, like characters on the drawings representing like parts.

This invention relates to the smelting of material bearing volatilizable metals particularly', but not exclusively, concentrated ores of zinc and has for its object the provision of a more efiicient and more economical method of smelting as practiced with retorts and condensers. advantageously but not necessarily practiced in connection with the process more fully described in my prior application, Serial No. 7561, filed Feb. 7, 1925.

My invention will be readily understood by reference to the following description thereof, more particularly when taken in connection, with the accompanying drawing illustrating diagrammatically a preferred process exemplifying the invention.

Before proceeding to the description ,of the process as such, it will be convenient to refer briefly to the furnace commonly used for the reductionof zinc ores or ores of. like volatilizable metals. Such a furnace includes tiers of cylindrical retorts as indicated in the diagram by the showing of one such retort at 3, these retorts being commonly made of fire clay or other suitable refractory material and being removably supported in thecombustion chamber of the The ores, oxides or sulphides converted to oxides by roasting, are mixed with the reduction fuel,

usually coal or coke free as far as possible from sulphur, and the mixture charged into the retort. In practice, when smelting zinc bearing ores the retorts are subjected to a temperature of about 1300 C. by externally applied heat which reduces the ore and being above the boiling point of zinc -volatil-- izes the metal, which passes out of the retort as a vapor and is condensed to a liquid in'a condenser 5, the latter consisting of a short frusto-conical continuation of the re- .tort projecting from the reduction chamber and being commonly detachably connected with the'retort.

In conducting the smelting operation it The invention iswhich may be metallic has been common practice to add common salt, sodium chloride, to the charge, for example, a weight of salt equal to about 2% of the weight of the roasted ore. The exact functions of the salt are not exactly understood but it is believed, first, that it acts as a binder on the charge, which is .desirable from the operating standpoint; second, that it acts as a flux to make the droplets of'zinc in the condenser coalesce third,

that it acts to remove the coatingof zinc oxide from the so-called blue powder; and fourth, that it materially amount of blue powder produced which would require re-smelting.

The introduction of chlorine into the charge by the use of salt produces, of course, a certain amount of zinc chloride which, being'volatilizable, isdischarged from the re- In accordance with my present invention I permit a substantial proportion of the vapors to pass from the mouth of the condenser and collect the metal values in these escaping vapors by deposit. Thus, in

the'diagram I have shown the end of .the'

condenser 5 as entering a hood 7 in which the vapors are preferably burned in a large excess of air to produce a fume product consisting largely of zinc oxide which may be led to a bag house or similar settling chamber, illustrated diagrammatically by the bag 9, wherein the metal values are recovered in the form of a owder or fume. As contrasted with prior processes in which the escape of vapors from the condenser was kept as low -as possible andrepresented a loss, I propose deliberately to operate the furnaceso that a substantial fraction of the metal values are passed from the mouth of the condenser and collected as a fume product. On account of the volatility of the zinc chloride it will be substantially entirel'y carried over in the fume product.. Zinc ores also may frequently contain a certain proportion of cadmium and a considerable portion of this metal will be selectively converted to chloride and be carried over into the fume product. Thus, for example, in a case where 2% of salt was utilized in the charge and the fume product collected contained 66.29% metallic zinc, 58.64% was prescut as zinc oxide and 7.65% as zinc chloride. In the same fume the cadmium content was 1.38%, all of which was'present'as chloride.

The step of the process just described may preferably be practiced in the manner dereduces the economical to attempt to recover.

scribed in my prior application referred to. Prior to the invention therein described good practice in smelting zinc ore was substantially as follows. The retort was loaded with mixed ore and fuel to roughly 75% of its cubical capacity. The recovery of metal content was about 89 4 64; in the formof spelter and of the remainder about 7.75% was in the residue. About 1% was absorbed by the walls of the retort and the condenser and the remaining loss of 1.7 5% was principally in the form of escaping vapors from the mouth of the condenser which it was un- In accordance with my invention as described in ,the said application, in order to permit more ore to be treated at one time and to increase the percentage of recovery of metal values minimizing the expense per unit of com mercially available metal produced, the retort is deliberately substantially overcharged beyond the capacity of the condenser to condense efficiently and preferably to its full. cubical capacity. Sufficient heat is applied to the retorts substantially to reduce all the metal in oxidized form and the condenser is operated at full condensing capacity for the given operating conditions to provide a large recovery of spelter while at the same time by the deliberate overcharge a substantial fraction of'themetal values isi intentionally caused to escape from the condenser to be recovered by deposit as a fume product.

By utilizing salt in an increased charge of this nature a large recovery of spelter may be provided for with the advantageous functions ofisalt as utilized in the prior art and the chloride will be collected substantially entirely in the fume product, as will also part of the cadminum value ifpresent. The presence of chloride in zinc oxide fume is undesirable since zinc chloride is a soluble salt. If only small quantities of chloride were present it would be possible to eliminate them by re-heating but if salt is used and large amounts of metal chloride recovered in the fume as above described, reheating is not a satisfactory method of purifying the fume. I therefore arrange to return the-chlorine values to the. furnace as a charge fora-subsequent volatilizing operation, thus economizingin the use of salt which after thefirst-inix need be added only to make up for operating losses, and increasing the percentage of zinc charged to the furnace as instead of salt containing no zinc, chloride of zine carrying a considerable quantity of metal is added in the same space. Furthermore, there is no substantial building up or increase in the relatively undesirable zinc chloride produced as' additional amounts of chlorine will not be supplied except as rendered necessary by operating losses.

Preferably the chlorine collected in the fume product may be returned to the retort for the subsequent volatilizing operation after recovery from the fume'of the valuable zinc oxide and such metal values as cadmium if present. Thus a preferred method of operation is illustrateddiagrammatically in the drawing. The fume product containing zinc oxide and various soluble chlorides may be leached with water, the chlorides appearing in the wash water and an insoluble residue remaining consisting of a very pure zinc oxide unchanged as to the size of par-' ticles and which needs only to be dried and disintegrated to restore it to its condition of a very fine zinc oxide free of chloride and other soluble salts and substantially free of lead and cadmium. If the quantity of cad lution is not a disadvantage since it is cus tomary and advantageous to wet down the charge of the furnace with water. The zinc chloride solution takes theplace of the water as well as of the salt and permits an in-.

creased charge of zinc per retort to the extent that the chloride solution bears zinc as compared with the water ordinarily used which carried no metal values and the salt which carries no metal values in the-commercialsense.

The zinc chloride solution is also admirably adapted for use as a binding agent and for this reason may be utilized in connection with reduction fuel and crude zincbearing material for the production of briquets, the briquetting of the charge increasing the amount of metal values that may be charged into a retort of given capacity.

-I have described in detail one particular series of operations exemplifying the method of my invention. Obviously these may be widely varied, substituted for by others, added to and in part omitted'without departing fromthe principles of the invention.

\Vhat I claim and desire to secureby Letv ters Patent I shall express in the following claims.

1 A method of recovering metal 'values from crude zinc-bearing material which comprises volatilizing' the metal-contentof such material in the presence of chlorine,

condensing as metal a major portion of the a fume product containing vapors, collecting an additional portion as a fume product containing the major portion of the chlorine and mixing the chlorine bearing content of such fume with fresh crude material and fuel for a subsequent volatilizing operation. I

2. A method of recovering metal values from crude zinc-bearing material which comprises volatilizing the metal content of such material in the presence of chlorine, condensing as metal a major portion of the vapors, collecting an additional portion as a fume product containing the major portion of the chlorine, leaching the fume and mixing the Wash water material and fuel to provide a charge for a subsequent volatilizingoperation.

3. A method'of recovering metal values from crude zinc-bearing material which comprises volatilizing the metal content of such material in the presence of chlorine, condensing as metal a major portion of the vapors, collecting anladditional portion as I the major portion of the chlorine, leaching the fume, treating the wash water with zinc to precipitate other metals and mixing the zinc and chlorine recovered in the liquid residue with fresh crude material and fuel to provide a charge for a subsequent volatilizing operation.

-4. A method of recovering metal values from crude zinc-bearing material which comprises volatilizing the metal content of such material in the presence of chlorine,

condensing as metal a major portion of the vapors, collecting an additional portion as a fume product containing the major portion of the chlorine, leaching the fume, treating the wash water with zinc to precipitate other metals and mixing the remaining liquid with fresh crude material and fuel to provide a charge for a subsequent volatilizing o eration. j 5. That method 0 recovering metal values from crude zinc-bearing materials which comprises volatilizing the metal content of such material in the presence of a salt which tends to prevent the formation of zinc oxide in the condensing metal vapors, condensing as metal a major portion of the vapors, collecting an additional portion as a fume product containing the radical of said salt and mixing the material containing said radical recoveredin said fume product with fresh crude material for a subsequent volatilizing.

operation.

6. A method of recovering metal values,

from crude zinc-bearing material which comprises volatilizing the metal content of such material in the presence of chlorine-,-

condensing as metal a major portion of the vapors, collecting an additional portion as a fume product containing the major portion of the chlorine and mixing such fumewith fresh crude material and fuel to prowith fresh crude.

as a fume product the vapors escaping from i the condensor, in which said fume product is contained at least a considerable portion of i the chlorine, and mixing the fume with fresh crude material and reduction fuel to provide a charge for a subsequent similar operation having a proportion of chloride provided through said fume.

8. That method of smelting crude zincbearing material utilizing a retort furnace and condensor which comprises :charging' the retort with a mixture of said material and reduction fuel together with a quantity of chloride in substantial. excess of the capacity of the condensor to condense fully the resultant metal vapors, collecting by deposit as a fume product the vapors escaping from the condensor and mixing the chloride recovered in said fume with fresh crude material and reduction fuel to provide a charge for a subsequent similar opera-- tion.

9. That method of smelting crude zincbearing material utilizing a retort furnace and condensor which comprises :-charging the retort with a mixture of said material and reduction fuel together with a quantity of chloride in substantial excess of the capacity of the condenser to condense fully the resultant metal vapors, collecting by de osit as a fume product the vapors escaping from the condensor, separating the chloride from said fume product and mixing it with fresh crude material and reduction fuel to provide a charge for a subsequent similar operation.

10. That method of smelting crude zincbearing material utilizing a retort furnace and condensor which comprises :charging the retort with a-mixture of said material and reduction fuel together with a quantity of chloride in substantial excess of the capacity of the condensor to condense fully the resultant metal vapors, collecting by deposit as a fume product the vapors escaping from the condensor, separating the chlorine from saidfume product as zinc 11. That methodof smelting crude zincbearing material utilizing a-retort furnace 4 and condensor which comprises :-char'ging the retort with a mixture of said material and reduction fuel together with aquantity of chloride in substantial excess of the capacity of the condensor to condense fully theresultant metal vapors, collecting by deposit as a fume product the vapors escaping from the condensor, leaching the chloride from said fume product and utilizing the wash water in preparing from fresh crude material and reduction fuel a charge for a subsequent similar operation.

12. A method of smelting crude zincbearing materials by the use of a retort furnace and condensor characterized by preparing from zinc-bearing materialand reduction fuel a mix of suitable consistency by the addition of a solution of zinc chloride, filling the retort substantially to its full cubical capacity withsuch mix, heating the preparing from zinc-bearingj material and reduction fuel a mix of suitable consistency bythe addition of a solution of a salt of zinc which tends to prevent the for mation' of zinc oxide in the condensing metal vapors, filling the retort substantially to its full cubical capacity with such mix, heating the retort, and collecting a substantial fraction of the metal values by deposit from the p'acity of the condensor "deposit as a fume product vapors escaping from the mouth of the condensor.

14. A method of recovering metal values from crude zinc-bearing material which comprises volatilizing the metal content of such material .in the presence of chlorine,

condensing as metal a major portion of the vapors, collecting an additional portion as a fume product containing the major portion of thechlorine, leaching the fume, mixing the wash water with fresh crude material and fuel and briquetting the mixture to provide a charge for a subsequent volatilizing operation.

15. That method of smelting crude zincbearing material utilizlng a retort furnace and condensor which comprises :charging' the retort with a mixture of said material and reduction fuel together with a quantityof substantial excess of the cato condense fully the resultant metal vapors, collecting by a the vapors esleaching the chloride in caping from the condensor,

chloride from said fume product, mixing the wash water with fresh crude material and fuel and briquetting the mixture to provide a charge for. a subsequent, volatilizing operation.

In testimony whereof, I have signed my name to this specification.

,WIILLIIAM noes. 

